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    SubjectRe: [PATCH/RFC] New module refcounting for net_proto_family
    Date
    In message <5.1.0.14.2.20030218101309.048d4288@mail1.qualcomm.com> you write:
    > At 07:46 PM 2/17/2003, David S. Miller wrote:
    >
    > >After talking to Alexey, I don't like this patch.
    > >
    > >The new module subsystem was supposed to deal with things
    > >like this cleanly, and this patch is merely a hack to cover
    > >up for it's shortcomings.

    I don't quite understand.

    There are some issue with this patch, however.

    Firstly, the owner field should probably be in struct proto_ops not
    struct socket, where the function pointers are.

    The sk thing looks reasonable at first glance. Getting a reference to
    npf->owner, then holding it for the socket is a little confusing, but
    an obvious optimization over a naive "get, use, drop, get".

    In sys_accept:

    > @@ -1196,9 +1198,13 @@
    > if (!(newsock = sock_alloc()))
    > goto out_put;
    >
    > - newsock->type = sock->type;
    > - newsock->ops = sock->ops;
    > + newsock->type = sock->type;
    > + newsock->ops = sock->ops;
    > + newsock->owner = sock->owner;
    >
    > + try_module_get(sock->owner);
    > + newsock->owner = sock->owner;
    > +
    > err = sock->ops->accept(sock, newsock, sock->file->f_flags);
    > if (err < 0)
    > goto out_release;

    You still need to check the result of try_module_get, and fail if it
    fails. The *only* time this will fail is when someone is doing an
    "rmmod --wait" on the module, which presumably means they really do
    not want you to increase the reference count furthur.

    Hope that helps,
    Rusty.
    --
    Anyone who quotes me in their sig is an idiot. -- Rusty Russell.
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